Ligaments are the fibrous tissue that connects bones to other bones within the body. When ligaments are damaged, surgical reconstruction can be necessary, as the ligaments may not regenerate on their own. One example is a knee 100 shown in FIG. 1, which includes anterior and posterior cruciate ligaments 102, 104 extending from a head of a tibia 106 to an intercondylar notch of the femur 108. These ligaments 102, 104 operate to prevent forward and backward relative motion between the two bones 106, 108. When ruptured (e.g., as can happen in strenuous athletic movements), surgical reconstruction can be necessary.
Tears in the cruciate ligaments of the knee can be repaired using a ligament graft taken from a cadaver (i.e., an allograft) or from a patient's own tissue (i.e., an autograft). Surgeons can reconstruct a cruciate ligament using either a ligament graft from a hamstring, or using a so-called “bone tendon bone” graft that harvests a portion of a patellar tendon 110 (along with plugs of bone at either end from a patella 112 and the tibia 106). More recently, the use of hamstring tissue for ligament grafts has grown more popular.
Reconstruction procedures generally involve forming a hole in both the femur and tibia, and then securing opposite ends of the ligament graft in these holes using an interference screw. One common technique, illustrated in FIG. 2 and known as the “high noon” approach, involves drilling a straight-line hole through the tibia from an inferior medial (i.e., lower and inner) surface thereof and extending almost straight upward through the femur (as shown by line 202). However, this technique can be disadvantageous in that it does not place the ligament graft in the ideal anatomical location, and therefore suffers reduced biomechanical effectiveness.
Another common technique for reconstruction of the cruciate ligaments is known as the “anteromedial” approach. As illustrated in FIG. 3, this technique involves forming a hole in the tibia 106 as described above, but the hole does not extend into the femur 108. Rather, a second hole is formed in the femur 108 along an anteromedial axis 302 of the femur 108. In particular, a hole is formed by drilling into a lateral condyle 304 of the femur 108 from a medial (i.e., inner) surface thereof. This technique can also have disadvantages, however. For example, approaching the lateral condyle 304 along the anteromedial axis 302 can pose a significant risk of contacting and damaging cartilage on a surface of a medial condyle 306. Furthermore, there is often no way to visualize the approach from within the knee (e.g., to assure the medial condyle 306 is not contacted).
A third technique for reconstruction of the cruciate ligaments is known as the “outside in” approach, and involves forming a hole in the femur 108 along the anteromedial axis 302 extending from a lateral surface of the femur 108 (i.e., entry point coming from the opposite of the “anteromedial” approach described above). To date, however, this approach has been mainly limited in that only “bone tendon bone” ligament grafts could be used—the use of increasingly popular hamstring ligament grafts has been possible only in a few limited cases.
Accordingly, there is a need for improved devices and methods for positioning and securing ligament grafts.